This invention generally relates to a technique which is used to produce cavitation and/or sonoluminescence in liquids.
It is well known that high velocity motion in a liquid can cause cavitation, or bubbles in the liquid. Many diverse mechanisms, e.g. propellers in water or ultrasonic sound waves, have been observed to cause such cavitation. Ultrasonic sound waves can produce not only cavitation but also a phenomenon known as sonoluminescence, which is the emission of light from the gas in cavitation bubbles.
In 1990, a paper was published by F. Gaitan and L. Crum, (see "Sonoluminescence from Single Bubbles" T. Acoust. Soc. AM. Suppl. 1, 87, 3141 (1990)) in which they reported that it is possible to capture a single small bubble of gas in the interior of a volume of water in which there existed a standing sound wave. This volume of water was excited at its fundamental vibrational mode. The bubble trapped in the center of the volume of liquid was shown to emit light. This phenomena goes by the name of "Single Bubble Sonoluminescence." Since that time, much experimental and theoretical work has been done on single bubble sonoluminescence, and there is now an extensive literature on the subject.
The following are representative of the papers that have been written and they contain extensive references to other earlier published work:
"Synchronous Picosecond Sonoluminescence," Ph.D, Dissertation of Bradley Paul Barber, UCLA Physics Department, Los Angeles, Calif. (1992)
"Sensitivity of Sonoluminescence to Experimental Parameters," B. P. Barber, C. C. Wu, R. Lofstedt, P. H. Roberts, and S. J. Putterman, Physical Review Letters, Volume 72, Number 9, Feb. 28, 1994, pages 1380-1383
"A Model of Sonoluminescence," C. C. Wu and P. H. Roberts, Proceedings of the Royal Society of London, A (1994) 445, pages 323-349
"Sonoluminescence," L. A. Crum and R. A. Roy, Science, Volume 266, Oct. 14, 1994, pages 233-234
"Effect of Noble Gas Doping in Single-Bubble Sonoluminescence," R. Hiller, K. Weninger, S. J. Putterman and B. P. Barber, Science, Volume 266, Oct. 14, 1994, pages 248-250
The above-referenced articles and the references cited therein all describe similar technologies. In general, the technology typically involves using a resonant container filled with water as the central component. Then, using a well known acoustical technique, a transducer is attached or glued to the surface of the container to drive the container at its resonant frequency. Various techniques are disclosed for injecting a gas bubble into the water including using a stirring rod, shooting a stream of air into the water using a hypodermic needle, and passing a current through a wire that is immersed in the water.
Researchers have tried to increase the temperatures and pressures that are obtainable with the trapped bubbles that exhibit sonoluminescence. The focus in some of these efforts has been on reducing the amount of dissolved gases in the liquid. For example, the above article entitled "Effect of Noble Gas Doping in Single-Bubble Sonoluminescence" by Hiller et al., who have looked in achieving sonoluminescence in nonaqueous fluids such as alcohol and silicon oil, states the following:
In nonaqueous fluids, we have been able to trap (nonlight emitting) air bubbles with sound, but at high drive levels, these systems have resisted our attempts to observe the transition to SL [sonoluminescence-ed.]. We propose that this difficulty is related to the unusually low solubility of gases in water (6), or equivalently to the fact that air is far more soluble in nonaqueous fluids such as alcohol and silicon oil.
Similarly, in another reference, namely the above-identified Ph.D. Dissertation entitled "Synchronous Picosecond Sonoluminescence", B. P. Barber notes that in order to obtain sonoluminescence in water it was first necessary to completely de-gas the water.
Some authors have also recognized that single-bubble sonoluminescence might be applicable to inertial confinement fusion. For example, in the above-referenced article entitled "Sensitivity of Sonoluminescence to Experimental Parameters", the authors write:
Assuming that these estimates would apply for a gas bubble which contains a mixture of deuterium and tritium, and that they remain physically valid at such minute length and time scales, the repetitive SL implosions generate about 1 n/s in such a mixture. Changes in the equation of state that these temperatures would bring about have also been ignored in making these estimates.
The neutron emission, N. was obtained from the standard formula [15] . . . . This computation yields about 40 n/s, but the results are very sensitive to the launch conditions, in part because a depends strongly on the conditions in a Van der Waals gas [16]."
This article calculates the fusion rate on the basis of an equilibrium temperature. As can be seen from the above quotation, this calculation yields a value for the neutron flux many orders of magnitude below any useful value for the generation of heat.